Delaney, Timothy C (Timothy) wrote:
> Guido van Rossum wrote:
>
>> I'd like the block statement to be defined exclusively in terms of
>> __exit__() though.
>
> 1. If an iterator declares __exit__, it cannot be used in a for-loop.
> For-loops do not guarantee resource cleanup.
>
> 2. If an iterator does not declare __exit__, it cannot be used in a
> block-statement.
> Block-statements guarantee resource cleanup.
Now some thoughts have solidified in my mind ... I'd like to define some
terminology that may be useful.
resource protocol:
__next__
__exit__
Note: __iter__ is explicitly *not* required.
resource:
An object that conforms to the resource protocol.
resource generator:
A generator function that produces a resource.
resource usage statement/suite:
A suite that uses a resource.
With this conceptual framework, I think the following makes sense:
- Keyword 'resource' for defining a resource generator.
- Keyword 'use' for using a resource.
e.g.
::
resource locker (lock):
lock.acquire()
try:
yield
finally:
lock.release()
use locker(lock):
# do stuff
Tim Delaney
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